The lone gunman behind Wednesday night’s deadly assault on a “college country night” party at a California bar has been identified as a former Marine, reports Fox News.

Investigators officially named the suspect as 28-year-old veteran Ian David Long just hours after he opened-fire at the Borderline Bar and Grill in Thousand Oaks, California; killing 12 people before turning the gun on himself.

“We’ve had several contacts with Mr. Long over the years, minor events such as a traffic collision. He was a victim of a battery in a bar in 2015,” confirmed Sheriff Geoff Dean.

Long served in the Marine Corps from August 2008 to March 2013 and was deployed in Afghanistan in November 2010 and June 2011.

“Obviously, he had something going on in his head that would cause him to do something like this. Obviously, he had some sort of issue,” added Dean.